physics :

Question 7 Calculate the minimum thickness (in nm) of an oil slick on water that appears blue when illuminated by white light perpendicular to its surface. Take the blue wavelength to be 467 nm and the index of refraction of oil to be 1.41. Your answer should be a number with one decimal place, do not include unit. 1 nm= 10-9111 Ind-=1 Question 8 Suppose you have a lens system that is to be used primarily for 698-nm red light. What is the second thinnest (in nm) coating of uorite (magnesium uoride) that would be nonreective for this wavelength? The index of refraction of the lens system is 1.5 and that of the uorite is 1.38. You should round your answer to the nearest integer, do not include unit